GUELPH — A new study from York University concludes that honeybees die sooner when exposed to field-realistic levels of a pesticide-treated corn seed known as neonicotinoids. But a similar European study was less critical.

The two-year York University study published in late June says bees exposed to field-realistic levels of neonicotinoids showed increased worker mortality and queenlessness. The study, which looked at fields in Ontario and Quebec, also finds that neonics acute toxicity (the effects from the pesticide that occur shortly after exposure) doubled in the presence of the fungicide boscalid.

The study discovered that most exposure of bees to neonicotinoids was actually not from the corn plants themselves, but plants in the environment. Croplife Canada declined comment on the study. The seeds treated with neonics were also treated with fluency agents designed to reduce the amount of neonic dust that escapes during planting, though the study didn’t track whether dust deflectors were used as well.

Public discussion and policy making on the pesticides have been dogged by the lack of data on neonicotinoids in field-realistic conditions and effects of the pesticide over time. The York University study “does address probably the most outstanding uncertainty, the longer-term assessment of neonicotinoids,” said University of Guelph environmental sciences professor Paul Sibley.

“The data are what they are, and they do show effects,” Sibley said. Not only in the season neonics are planted, but the data suggest effects can be season-over-season, due to persistence of neonics in the environment.

Former crop scientist and cash crop farmer Terry Daynard disagreed. He wrote an analysis of the study on his blog, saying that the conclusion of the study “is weakened seriously by data inconsistencies and deficiencies, major questions about bee management, and dubious statistical analyses. The potential role of varroa mites and other pests and diseases is ignored.”

A study that included the largest field trial ever conducted in Europe, published in the same journal on the same day, came to a slightly different conclusion than the York study. Although the study found that “agricultural use of these common pesticides can hurt both domesticated honey bees and wild bees,” it also discovered that some bees exposed to neonicotinoids “did just fine, suggesting that some colonies can weather the toxicity.”

Said Sibley: “If you’ve got a diverse landscape, one in which the bees can forage from a number of different sources, you actually didn’t see any effects. Even though there were residues, bees weren’t actually affected by the neonicotinoids. So the question is a bit more complicated than neonics’ toxicity.”

The European study from the Centre for Ecology and Hydrology in the United Kingdom delivered a “split verdict.” The summary of the study goes on to say that “mixed findings are likely to intensify ongoing debates about restricting or banning the compounds, with both sides claiming vindication.”

The data are not the knockout punches that either side was hoping for. Environmental activists have laid an albatross of environmental havoc on the neck of neonics and the farmers who use them, whereas neonic supporters have applauded the pesticide as a useful or even necessary tool for farmers. The Ontario government has been both applauded and decried over its restrictions on neonics, with environmental groups saying the government is protecting pollinators, and industry saying the government made decisions without the science to back them up.

Sibley said that neonicotinoid use definitely needs to be restrained and controlled. But a ban remains, in his mind, unreasonable and unnecessary. That’s because the European study results, where bees in some areas that were exposed to neonics struggled and in other areas did fine, lends credence to the idea that neonics can be used safely. “It suggests that there is the potential that neonics can be used at levels where, with other factors like greater foraging capacity, that we can mitigate this reduced wild bee health,” he said.

Ontario’s approach to neonics had its problems, said Sibley, but reducing usage was a step in the right direction. “We need a way to manage pesticides of all descriptions such that we use them as we need them. Not just apply them, then add a little extra, just to be sure.”